Analysis of transcription of N4 E. coli infected by pulse-labeling and hybridization has revealed the presence of two new RNA polymerizing activities. The first N4 activity, unprecedented, appears in cells treated prior to infection with both rifampicin (or streptolidigin) and chloramphenicol and therefore requires neither transcription by the E. coli DNA-dependent RNA polymerase nor translation of the phage chromosome. We have devised a method to measure this activity and propose to study it biochemically and genetically (with respect to host and viral involvement). The second activity, maximal 4-6 minutes after infection, is rifampicin and streptolidigin resistant and requires the proper expression and function of N4 genes. We propose to isolate and characterize it biochemically.